Lattice Gauge Theory at the Intensity Frontier

University Of Utah, Salt Lake City UT

Investigators

Abstract

This award funds the research activities of Professor Carleton DeTar at the University of Utah. Professor deTar's research addresses fundamental questions in high-energy and nuclear physics, and is closely related --- indeed, even essential --- to major experimental programs in these fields. The principal goal of this research is to discover evidence for new fundamental physical processes and particles. This is done by comparing precise predictions of theories of currently known physical processes and particles with the results of precise experiments. The methods that Professor deTar and his collaborators develop and their calculational products and software are used widely around the world for related studies. In addition to maintaining US excellence in fundamental science, this research supports US preeminence in computing technology and manpower. Students and postdoctoral research associates working on these projects receive highly marketable training in high-performance computing and state-of-the-art statistical analysis of large data sets. In more technical terms, Professor deTar and his collaborators are carrying out a broad research program in Quantum Chromodynamics (QCD), the theory of interacting quarks and gluons. They do this using numerical calculations on high-performance computers. These numerical calculations are done on a grid of space-time points (lattice). During the last several years they have generated a library of gluon-configuration ensembles with up, down, strange and charm quarks, using the highly improved staggered quark (HISQ) action. These gluon configurations can be thought of as "snapshots" of the QCD vacuum, and are the basis for a wide variety of calculations of physical interest. These ensembles have significantly smaller lattice artifacts than those they previously generated with the improved staggered (asqtad) action. Moreover, these calculations have reached an important milestone by generating, for the first time, configurations in which the four lightest quarks are all included with masses at or very close to their physical values. For these reasons the HISQ ensembles are enabling major improvements in the calculation of a variety of physical quantities of importance in high-energy physics, including the strong-interaction contributions to the magnetic moment of the muon. Results of these Standard-Model predictions will be checked against experimental measurements currently underway at Fermilab. Professor deTar and his collaborators are also extending their studies of the leptonic decay constants of the pi, K, D, Ds, B and Bs mesons, the semileptonic form factors of D and B mesons, and the mixing of neutral B and Bs mesons with their antiparticles. These calculations will enable them to significantly improve the precision of their determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements V_us, V_ub, V_cd, V_cs, and V_cb, as well as the masses of the up, down, strange, charm and bottom quarks. The calculations of the CKM matrix elements will provide more stringent tests of our current theories of the fundamental interactions of physics, while the determination of related hadronic weak-interaction matrix elements can help constrain theories that have been proposed to study physics that goes beyond our current theories.